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Tom Lane 7c15cef86d Base information_schema.sql_identifier domain on name, not varchar. 
The SQL spec says that sql_identifier is a domain over varchar,
but it also says that that domain is supposed to represent the set
of valid identifiers for the implementation, in particular applying
a length limit matching the implementation's identifier length limit.
We were declaring sql_identifier as just "character varying", thus
duplicating what the spec says about base type, but entirely failing
at the rest of it.

Instead, let's declare sql_identifier as a domain over type "name".
(We can drop the COLLATE "C" added by commit 6b0faf723, since that's
now implicit in "name".)  With the recent improvements to name's
comparison support, there's not a lot of functional difference between
name and varchar.  So although in principle this is a spec deviation,
it's a pretty minor one.  And correctly enforcing PG's name length limit
is a good thing; on balance this seems closer to the intent of the spec
than what we had.

But that's all just language-lawyering.  The *real* reason to do this is
that it makes sql_identifier columns exposed by information_schema views
be just direct representations of the underlying "name" catalog columns,
eliminating a semantic mismatch that was disastrous for performance of
typical queries on the information_schema.  In combination with the
recent change to allow dropping no-op CoerceToDomain nodes, this allows
(for example) queries such as

    select ... from information_schema.tables where table_name = 'foo';

to produce an indexscan rather than a seqscan on pg_class.

Discussion: https://postgr.es/m/CAFj8pRBUCX4LZ2rA2BbEkdD6NN59mgx+BLo1gO08Wod4RLtcTg@mail.gmail.com
2018-12-20 16:21:59 -05:00
config Update config/ax_pthread.m4 to latest upstream version. 2018-11-19 15:05:33 -05:00
contrib Update sepgsql regression test results for commit ca4103025. 2018-12-18 11:40:10 -05:00
doc Doc: fix ancient mistake in search_path documentation. 2018-12-20 13:55:11 -05:00
src Base information_schema.sql_identifier domain on name, not varchar. 2018-12-20 16:21:59 -05:00
.dir-locals.el Update documentation editor setup instructions 2018-07-13 21:23:41 +02:00
.gitattributes Remove contrib/tsearch2. 2017-02-13 11:06:11 -05:00
.gitignore Support for optimizing and emitting code in LLVM JIT provider. 2018-03-22 11:05:22 -07:00
aclocal.m4 Fix configure's AC_CHECK_DECLS tests to work correctly with clang. 2018-11-19 12:01:47 -05:00
configure Drop support for getting signal descriptions from sys_siglist[]. 2018-12-17 13:50:16 -05:00
configure.in Drop support for getting signal descriptions from sys_siglist[]. 2018-12-17 13:50:16 -05:00
COPYRIGHT Update copyright for 2018 2018-01-02 23:30:12 -05:00
GNUmakefile.in Remove unwanted "garbage cleanup" logic in Makefiles. 2018-08-08 14:32:29 -04:00
HISTORY Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
Makefile Fix non-GNU makefiles for AIX make. 2017-11-30 00:57:22 -08:00
README Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
README.git Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00

README 

PostgreSQL Database Management System
=====================================

This directory contains the source code distribution of the PostgreSQL
database management system.

PostgreSQL is an advanced object-relational database management system
that supports an extended subset of the SQL standard, including
transactions, foreign keys, subqueries, triggers, user-defined types
and functions.  This distribution also contains C language bindings.

PostgreSQL has many language interfaces, many of which are listed here:

	https://www.postgresql.org/download

See the file INSTALL for instructions on how to build and install
PostgreSQL.  That file also lists supported operating systems and
hardware platforms and contains information regarding any other
software packages that are required to build or run the PostgreSQL
system.  Copyright and license information can be found in the
file COPYRIGHT.  A comprehensive documentation set is included in this
distribution; it can be read as described in the installation
instructions.

The latest version of this software may be obtained at
https://www.postgresql.org/download/.  For more information look at our
web site located at https://www.postgresql.org/.